1. Related Applications
This application is related to Ser. No. 08/522,123 filed Aug. 31, 1995, the entire contents and disclosure of which is incorporated herein by reference.
2. Field of the Invention
The invention relates to stain-resistant polyamide compositions and fibers and articles of manufacture formed therefrom.
3. Description of the Prior Art
Textile and carpet yarns prepared from polyamide fibers are subject to staining by a variety of foods, drinks and many other compositions with which it comes in accidental contact. The uptake of acid dye stains from, for example, soft drinks, is a particularly vexing problem for polyamide fibers due to the availability therein of acid dye sites such as amine end groups and amide linkages. Several methods have been suggested for enhancing the resistance of polyamide fibers to acid dye stains.
One approach is to apply a so-called "stain blocker" coating to the surfaces of polyamide fibers to prevent access to the acid dye sites therein by the acid dye staining composition. An example of such a method is illustrated by U.S. Pat. No. 5,145,487 which discloses coating the fibers with sulfonated aromatic condensates (SACs). Similar proposals are suggested in U.S. Pat. Nos. 4,680,212 and 4,780,099.
Another approach is to form the fibers from polyamides prepared by copolymerizing monomers, some of which contain sulfonate moieties. Typical of such systems are those disclosed in U.S. Pat. Nos. 3,542,743; 3,846,507; 3,898,200 and 5,108,684.
U.S. Pat. No. 4,374,641 relates to pigment concentrates made using sulfonated polymers as carrier resins including the highly sulfonated polyamides disclosed in U.S. Pat. No. 3,846,507. U.S. Pat. No. 5,236,645 represents an improvement on the invention claimed in U.S. Pat. No. 4,374,641.
Fibers are generally prepared from polyamides by melt-spinning. Sulfonate containing copolymers generally have higher melt viscosities than non-sulfonate containing copolymers for equivalent relative solution viscosities which limits the extent of polymerization which can be achieved in batch autoclave reaction vessels due to the retardation thereby of the rate of polymerization, as well as its hindrance of effective discharge of the polymerized melt from the reactor. In addition, the presence of sulfonates which have surfactant properties promotes excessive foaming during the melt polymerization process, resulting in poor agitation of the reaction mixture and non-uniformity of product.
Yarns having different depths of color require different levels of stain protection. Thus, light shaded colors show the presence of stains more than darker colors. It would be advantageous, therefore, to be able to provide different levels of stain resistance to polyamides depending upon the ultimate yarn color without having to provide a separate polyamide feedstock for optimum formulation of each color yarn.
An additional disadvantage associated with sulfonate containing polyamide copolymers is that they are generally more difficult to dry than sulfonate-free polyamides due to the hygroscopic nature of sulfonate groups.
Polyamides that are topically coated to give stain resistance to the fiber, e.g., with SACs, have the disadvantage that the topical coating is removed during use and maintenance. Gradual removal of the coating will also occur during cleaning with water and detergents. Fibers used for carpet applications may be regularly cleaned with alkaline-based cleaning agents. SAC topical coatings are easily removed using these types of cleaning agents. The topical coating will also be gradually removed during normal wear of the fiber in its chosen application. In addition to their removal during use and maintenance, SACs generally have inferior resistance to light, oxides of nitrogen, and bleach, the latter of which is commonly used for the cleaning of industrial textiles and carpets. Also, the base color of SACs is not colorless and thus may change the shade of the color of the yarn.
In copending application Ser. No. 08/522,123 filed Aug. 31, 1995, there is disclosed an acid dye stain-resistant fiber-forming polyamide composition comprising a fiber-forming polyamide and a reagent, at least a portion of which associates with free acid dye sites in the polyamide, thereby disabling those acid dye sites in fibers formed from the composition from taking up acid dye stains.
Also disclosed therein are masterbatch concentrates for addition to a fiber-forming polyamide to form the above-described acid dye stain-resistant fiber-forming polyamide composition, the concentrate comprising a carrier material compatible with the fiber-forming polyamide, preferably a polyamide, combined with an amount of the reagent in excess of that desired in the acid dye stain-resistant fiber-forming polyamide such that addition of the concentrate to the compatible fiber-forming polyamide results in the desired level of stain resistance.
A disadvantage associated with the compositions and methods of the earlier application is that there are limitations in the amount of reagent which can be incorporated or "loaded" into the masterbatch concentrate utilizing the carrier materials disclosed, in particular, the polyamide carriers, indicated as preferred carrier materials, therein. It has been found that it is difficult, if not impossible, to achieve 20% or higher weight loadings of reagent in masterbatch concentrates using the preferred polyamide carriers. This is due to the fact that the melt viscosity of the resulting mixture is lowered significantly by these higher loadings of reagent, making it very difficult to produce and pelletize extrudates therefrom for incorporation into the fiber-forming polyamide. Moreover, the color of the masterbatch concentrates produced therefrom tend to be discolored yellow, thereby affecting the shade of the ultimately desired fiber color.
Most significantly, the melt viscosities of these higher loaded masterbatch concentrates are markedly lower than those of the fiber-forming polyamides such that when the masterbatch concentrates are diluted or incorporated in the polyamide feedstocks on-line in typical melt-spinning systems, the lowered melt viscosity of the resulting mixtures results in poor spinnability.
It is an object of the present invention to provide improved masterbatch concentrates containing stain-resist imparting reagents for incorporation in fiber-forming polyamides which enable efficient fiber-forming methods and systems that incorporate higher stain-resist reagent loadings in the fibers than heretofore possible.